Simulator: implement own random generator instead of scipy
Simulator: implement own random generator instead of scipy

Dependency on scipy results in extra requirements to the system
(include the need of Fortran compiler). With this patch the
weighted random choice algorithm is implemented directly.

Change-Id: I60cbc6c452945000add5a65263d1ab4e42dd91f9

ozamiatin/oslo.messaging,ozamiatin/oslo.messaging